Electric system for motor vehicles



T. L. LEE.

ELECTRIC SYSTEM FOR MOTOR VEHICLES.

APPLlCATlON HLED NOV. 4, 1919.

1,40 ,039, Patented'Feb. 7, 1922.-

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ELECTRIC SYSTIHI FOR MOTCR VEHICLES.

Specification of Letters Patent.

Application filed November 4 19 19. Serial-No, 885,689.

To all whom it may concern:

Be it known that I, THOMAS L. Iran, a citizen of the United States,resid ng at Rochester, in the county. .of Monroe and State of New York,have invented certa n new and useful Improvements in Electric Systemsfor Motor Vehicles; and I do here- In such a system a short-circuit isliable' to occur, through carelessness on the part of the user orthrough defects in the insulation of the system, with seriousconsequences to the circuit-conductorsor the source of current.

A common way to safe ard an electric system against short-circults is tointerpose a fuse in a main conductor of the system. But a fuse, used inthe ordinary manner, is undesirable in the electric system of amotor-vehicle for two reasons. In the first place, the user of thevehicle is likely to fail to provide spare fuses, with the result thatwhen the fuse has blown, inconsequence of a short-circuit, he is unableto restore the system to operation, even though the cause of theshort-circuit hasbeen removed or was merely temporary in, its nature. Inthe second place, the cause of the short-circuit may be intermittent,but so obscurely located as not to be readily. detected and removed.

The object of the present invention is to provide an electric system, ofthe kind in question, with a simple and reliablelgievice which willsafe-guard it against the detructive eifects of a short-circuit, butwhich will permit continued operation of the system, without thenecessity of renewing a fuse, or any other attention on the part of theuser, whenever the cause of the short-circuit has been removed or ismerely temporary or intermittent.

To the foregoing end it is proposed, to interpose, in a main conductorof the system, a fuse adapted to blow upon the occa'srrence of ashort-circuit, but to connect in parallel with the fuse aresistance-device so Patented Feb, '7, 1922.

adjusted as to permit a flow of current sufy ficient for the continuedoperation of some or all the translating-devices of the system, I

but not sufficient to unduly load or discharge the battery or othersource of current.

In the accompanying drawings Fig. 1 is a front-elevation, and Fig. 2 aside-elevat1on, of a protective devlce comprising a combined fuse andresistance-unit adapted for use 1n carrying out the present invent1on,and Fig. 3 is a diagram of an electric system embodying the invention.

In F g. 3 the system is shown as comprismg two sources of current,namely, a generator 5 and a storage-battery 6, which are connected inparallel, in the usual manner, to the two main conductors 7 and 8 of thesystem. A switch 9, interposed in the conductor 7, may be used todisconnect the generator when it is not in operation.

In the illustrated system thetranslating devices lnclude a pair ofhead-lights 10 controlled by a switch 11, a tail-light 12 controlled bya, switch 13, and electric ignition apparatus 14, of conventional form,controlled by a switch 15.

The protective device characteristic of the invention comprises a fuse16 and a resistance-device 17, which are connected, in parallel, to twocommon terminals 18 and interposed in the main conductor 7 between thetranslating devices and the sources of current. This arrangement is suchthat if the 'fuse be blown the resistance-device will still conduct acertain amount of current to the translating devices.'

The capacity of the fuse and the resistance of the resistance-device areadjusted according to the characteristics'of the other parts of thesystem, the capacity of the fuse being substantially above the normalmaximum load imposed by the translating devices, but substantially belowthe amount necessary to dangerously overload the source of current orthe conductors of the system. The resistance-device has conductivitysufficient to pass a current which will permit continued operation ofthe translating devices, or at least of the more essential ones, butsufficient resistance to prevent dangerous overloadin in the case of acontinued short-circuit. ere the source of current is a battery theresistance is referably such as to limit the discharge, t rough a con-'tinued short-circuit, to an amount which will not deplete the batterduring a period of several hours, thus a ording time .forthe discoveryand removal of the cause of theshort-circuit before the system isrendered inoperative by reason of the exhaust on of the current-supply.

As a specific instance of a system success v fully embodying theinvention, the system shown in Fig. 3 may be provided wlth a six-cellstorage-battery,maintaining a m1n1- mum of approximately 12 volts acrossthe main conductors 7 and 8 when the system is in operation. The.head-lights may be of 15 c. p. each, theresistance of thetwo lamps inseries being about6 ohms. The tall-lamp may be of 4 c. p., with aresistance of 36 ohms, while the resistance of the primarycircuit of theignition-apparatus, apart from the reactance of the coil or transformer,may, be about 6 ohms. The resistance .of the connecting wires maynegligible. t

In a system as just described the fuse 16 may be of 10 amperes nominalcapacity, and the resistance-device 17 may have a resistance of about 3ohms. It should alsobe capable of dissipating indefinitely the heatresulting from a continuous current of 5 amperes, since thegenerator,when operating, may produce. an E. M. F. of about 15 volts across themain conductors.

With a resistance of 3 ohms in the resistbe. so low as to be ance-devicethe maximum rate of discharge of the battery6 onshort-circuit, after thefuse 16 has blown, is limited to about 4 amperes, and the battery, if ofthe size and type ordinarily used in systemsof the kind in question,will sustain this dlscharge for several hours unless alread in adischarged condition when the short-circuit occurs. If the short-circuitis removed or is merely intermittent in character, the translatingdevices will continue to operate by the current flowing through theresistance-device The ignition apparatus will operate withoutappreciable impairment of its efiiciency, for at high speeds the virtualresistance of the I apparatus, due chiefly to impedance, is so high thatthe 3 ohms of the resistance-device constitute only a smallproportionate increase.

The tail-light will also-operate with very little diminution of itsbrilliancy, since its resistance of 36 ohms is large in proportion tothat of the resistance-device.

The head-lights will be substantially dimmed by the additionalresistance of 3 ohms, but will still glow sufficiently to conform withlegal requirements and permit the operation of the vehicle at night.

A simple, compact and'convenient structure, by which the fuse and theresistancedevice are interconnected, and are embodied in aseuf-contained unit or instrument, is

shown in Figs. 1 and 2. This structure has a base-member consisting of asingle piece of sheet-metal and comprising a back-plate 19,v a shelf 20projecting horizontally from the lower end of the back-plate, and aflange 21 depending from the outer edge ofthe shelf. The resistance-unit22 is mounted on the shelf 20 and secured in place by a through-bo1t'23.The fuse 16 is held in clips 24 which are bolted to, but insulated fromthe front of the flange 21. The terminal-lugs 18 are directly engaged bythe fuse-clips, and are provided with arms 25 to whichthe ends of theresistance-wire 17 are soldered, thus connecting the resistance devicein parallel with the fuse through the terminal-lugs.

The back-plate has perforated depressed 1.

portions 26 which receive screws to secure the instrument in placeagainst a surface such as the dash of a vehicle, and'by means of thesedepressed "portions'the body of the back-plateis heldfclear of thesupport so as 'to-afi'ord free access ofthe air. to dissipate 1 heatconducted to the back-plate from the resistance-unit.

It will be apparent that the described specific construction of theresistance-unit and the fuse are not essential to embodiment of theinvention in .its broader aspects, also that the resistance and thecurrent-carrying capacity of these parts will necessarily be variedaccording to the characteristics of the system in which the invention isused. The invention is, therefore, not limited tothe embodiment thereofhereinbefore described, but it may be embodied in various other formswithin claims.

' l The invention claimed is:

the scope of the following 2. In am electric system for motor-vehi- Vcles, the combination, with a source of current, electric head-lights,anelectric taillight, and a conductor connecting the source of currentwith the lights, of a fuse interposed in the conductor; and aresistance-device connected in parallel with the fuse and having aresistance equal to approximately half the resistance of thehead-lights.

3. In an. electric system for motor-vehicles, thecombination of a sourceof current;

electric head-lights; electric ignition-appa-.

ratus; a common conductor connecting the source of current with thehead-lights and the ignition-apparatus; a fuse interposed in theconductor; and a resistance-device oon nected in parallel with the fuse;the resistance of the resistance-device being approximately half that ofthe head-lights and of the ignition-apparatus.

4. In an electric system for motor-vehicles, the combination, with astorage-battery, electric lights, electric ignition-apparatus, andacommon conductor connecting the battery with the electric lights andthe ignition-apparatus, of a fuse interposed in said main-conductor, anda resistance-device connected in parallel with the fuse.

5. In an electric system for a motor-vehicle, the combination, with asource of ourrgnt, translating-devices, and conductive in ohms, isapproximately three-tenths of the conductivity, in amperes, of the fuse.

THOMAS L. LEE.

